Polymeric materials are widely used in the field of implantable medical devices. Poly(ethylene terephthalate) (PET) in particular is widely used for implantable medical devices such as catheters, electrical lead bodies, surgical mesh, implantable sutures, vascular grafts, tissue scaffolds, tracheal tubes, and esophageal stents. PET has a long history of biostability and is one of only a few polymers approved for long term implant use in medical devices.
Incorporating PET into implantable medical devices may be done by a variety of methods, depending on the specific application. In some applications, PET may be extruded at a temperature sufficient to cause the PET to flow, but not high enough to cause the PET to break down. That is, the PET material forming the medical device after the extrusion and cooling has largely the same structure as the original PET material.
In other applications, it may be desirable to employ solvent-based processing to incorporate polymeric materials, such as PET, into an implantable medical device. Solvent-based processing includes electrospraying, electrospinning, spray coating, dip coating, and force spinning. Essential to all solvent-based processing of polymeric materials is the ability to bring the polymeric material into solution while retaining the basic structure of the polymeric material. In some cases, solutions of polymeric materials may be limited to only a few weight percent of the polymeric material (e.g. less than about 2 wt. %). Solutions having such low weight percent of polymeric material dissolved may not be economically useful in some solvent-base processing, and may not work at all in other solvent-based processing. In still other cases, it may be possible to bring a polymeric material into solution at adequate concentrations, but the solvent may be so acutely hazardous to humans or the environment that its use is undesirable.